Alcatel-Lucent v. Microsoft Corp., also known as Lucent Technologies Inc. v. Gateway Inc., was a long-running patent infringement case between Alcatel-Lucent and Microsoft litigated in the United States District Court for the Southern District of California and appealed multiple times to the United States Court of Appeals for the Federal Circuit.

Lucent claimed in this first San Diego case that Dell and Gateway had violated patents on MP3-related technologies developed by Bell Labs, a division of predecessor company American Telephone & Telegraph.

In February 2007, Microsoft filed a lawsuit at the International Trade Commission claiming that Alcatel-Lucent infringed its patents.

Reissue of 05627938 Filed: Sep., 1994 Granted: May., 1997[7] The first part of the San Diego case involved the '457 and '080 audio coding patents.

Alcatel-Lucent claimed that Microsoft's Windows Media Player infringed these patents by virtue of its MP3 capabilities.

The Court of Appeals published its decision [13] on September 25, 2008, upholding the dismissal of the case by Judge Brewster on two grounds.

The court held that Fraunhofer was a joint developer and thus co-owner of one patent, which meant that Lucent lacked standing to sue.

In April 2008, a jury awarded Alcatel-Lucent $367.4 million in damages after finding that Microsoft had violated two patents related to the user interface in its software.

In June 2008, the trial judge upheld the jury's verdict and increased the damage award against Microsoft to $512 million to account for interest.